Ice wedges grow as the ice-rich frozen ground contracts during the winter and forms open cracks below the surface. As the ground surface warms and the snow thaws in the spring, meltwater flows into the open cracks and freezes. But the ground beneath is still frozen, and as the freezing water expands, it forces the surrounding soil upward and outward. This process creates the ridges and troughs typically seen on either side of the ice wedges. Networks of ice wedges form the distinctive polygonal patterns that mark the surface of permafrost. These features, commonly found in areas of both permafrost and seasonal frost, are formed by contraction cracks enlarged by ice wedges.
From album: Sea Ice, Icebergs, Glaciers, Snow and Permafrost in the Arctic Region